Prevalence of Antimicrobial Resistant Pathogenic and Indicator Bacteria in Dairy Production Systems and Plant Based Milk

Winnie Wanja Mukuna, Tennessee State University


Antimicrobial resistance is undeniably among the greatest health challenges in the 21st century. This study compared antibiotic resistant patterns in dairy goat and cow production systems. Soil, water, manure, and milk samples were collected from two cow farms and one goat farm and analyzed for Enterobacteriaceae, E. coli O157:H:7, Listeria spp, Salmonella serovar, Campylobacter spp and Enterococcus spp using molecular and biochemical techniques. All Enterobacteriaceae species 100% resistant novobiocin, erythromycin, and vancomycin. NOV-TET-ERY-VAN was the most common (p < 0.05) profile observed in 113 of the 148 isolates from manure, soil and water. Cow and goat milk displayed five antimicrobial profiles, the most common being NOV-TET-ERY-VAN. Listeria spp, Enterococcus spp, E. coli O157:H7, Salmonella serovar, and Campylobacter spp were not detected in either cow or goat milk. Listeria spp, Enterococcus spp, E. coli O157:H7, Salmonella serovar isolates from the environment were multidrug resistant. E. coli O157:H7 and Salmonella serovar displayed three and five different profiles respectively. The most common profile in Enterococcus spp was VAN-NOV-ERY profile, while Listeria spp displayed 10 resistant profiles. Since current lifestyle changes have popularized plant-based milk, this study also evaluated prevalence of antimicrobial resistant Enterobacteriaceae in almond, cashew, and soymilk. Additionally, the effect of abusive (23 ºC) and cold storage (4 ºC) temperature on the growth of Listeria spp, Salmonella typhimurium, and E. coli O157:H7 in almond, cashew, soy, cow and goat milk was studied. A total of 111 Enterobacteriaceae were identified. Enterobacter cloacae (42.3%) and Enterobacter cancerogenus (35.1%) were the most common species (p < 0.05). The highest resistance (p < 0.05) was observed in vancomycin (88.3%) and novobiocin (83.8%). Although all milk types provided a good medium for bacterial growth, soy milk was the best medium for all three bacteria at 23 ºC. At 4 ºC, Salmonella typhimurium and E. coli O157:H7 displayed negative growth rates while Listeria spp growth gradually increased during the nine-day storage period. Data from this study suggest that dairy production systems and plant-based milk are reservoirs of antimicrobial resistant bacteria. Additionally, consumers should properly store their milk at 4 ºC to decelerate bacterial growth.

Subject Area

Food Science|Microbiology|Agriculture

Recommended Citation

Winnie Wanja Mukuna, "Prevalence of Antimicrobial Resistant Pathogenic and Indicator Bacteria in Dairy Production Systems and Plant Based Milk" (2020). ETD Collection for Tennessee State University. Paper AAI27829449.